[Tutor] Change datatype for specific columns in an 2D array & computing the mean

[Ek Esawi]

Here is the file.

AA,BB,CC,DD,EE

1,A1,B1,11.2,11/20/2011

2,A2,B2,2.5,10/21/2011

3,A3,B3,13.67,9/21/2011

4,A4,B4,14.2,8/22/2011

5,A5,B5,20,7/23/2011